BRUSSELS, Belgium -- Capitals across Europe celebrated Friday night and into Saturday morning as the European Union marked the largest expansion in its history.

Ten new members, eight of them formerly under communist rule, joined the EU at midnight CET (2200 GMT), but celebrations began earlier in countries farther east. The accession unites Eastern and Western Europe, patching rifts left by World War II and the Cold War.

The new member states are Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia. The additions bring the EU's population to 450 million, making it the world's largest trading bloc.

At the Italian-Slovenian border, European Commission President Romano Prodi presided over a reunification ceremony in the Italian town of Gorizia and the Slovenian town of Nova Goricia, divided by an iron fence since the end of World War II.

Prodi said, in Italian, "Today's enlargement is the fifth and the largest in the history of the union, and I am convinced that it will not be the last. Other European countries and nations will decide to join our undertaking until the whole continent is unified in peace and democracy," Reuters reported.

In Poland, the largest new EU member, a chorus sang in a Warsaw square and a video screen showed scenes of Poland's climb from post-World War II destruction through communist domination to democratic rule.

President Aleksander Kwasniewski told the crowd, "Ladies and gentlemen, we are making history ... Today our dream is becoming reality. Poland is returning to its European family," Reuters reported.

At the German-Polish border, the hoisting of the EU flag was accompanied by fireworks and the "Ode to Joy" from Beethoven's Ninth Symphony.

A two-hour concert at the Berliner Konzerthaus and an open-air stage in Warsaw symbolically linked the two cities, and featured performers from the newest EU states.

In Malta, part of "Ca Ira (It Will be Fine)," a new opera by former Pink Floyd singer Roger Waters, was accompanied by lasers, floodlights and fireworks. Giant images were projected on the city's historic fortress walls, and boats with sails representing EU members' flags floated below.

The Berlin, Warsaw and Malta concerts were part of the celebration arranged by the EU, and were carried on live television in 30 countries.

"We are not expecting charity," one Lithuanian reveler speaking English told Reuters. "We are hard-working people, and we will work, we will catch up with the rest of Europe, and quite soon we will do it."

In Cyprus, Greek Cypriots celebrated the event, but Reuters reported that reaction was muted in the island's north, where the breakaway Turkish cypriot state was left behind after a reunification vote failed last week.

On Saturday, the leaders of all 25 EU countries will gather for a largely ceremonial summit in Dublin. The Republic of Ireland holds the six-month rotating EU presidency.

On the eve of the celebrations, Prodi declared that the divisions of the Cold War had been removed once and for all.

"We are bringing into the EU family 10 new member states and 75 million new EU citizens," the UK Press Association quoted Prodi as saying.

"Five decades after our great project of European integration began, we are celebrating the fact that Europeans are no longer kept apart by artificial ideological barriers.

"We share the same destiny and we are stronger when we act together. I urge all Europeans to join in celebrations of this astonishing achievement."

The commission is spending about 6 million euros ($7 million) on the enlargement celebrations.

The EU began with six member states, becoming nine in 1973 with the arrival of the UK, Ireland and Denmark.

Greece followed in 1981, and Portugal and Spain in 1986. Austria, Sweden and Finland made in 15 in 1995.

"May 1 will be a milestone in the history of Europe," EU Enlargement Commissioner Guenter Verheugen said.

"It is Europe's response to the end of the Cold War and an opportunity to heal the wounds of the past, wounds of war and dictatorship," Reuters quoted Verheugen as saying in Warsaw.

The enlargement crowns efforts by Poland and Germany to overcome the past. They are the largest old and new members of the EU, with about 80 million and 40 million citizens, respectively.